Telephone systems are known which provide a common interface between a plurality of users and a public telephone network. These systems have been referred to as PBX systems. A typical PBX system includes a central box with line cards providing connections to assigned lines of the PSTN network. The central box is connected by wires such as twisted pair wires to individual telephone units. The connection from the central box to the telephone units may be by way of analogue or digital signals. More recently, digital signals are sent by the central unit to the phone units. The digital signals include voice data as well as control and messaging data. The units typically include a simple handset as well as a speaker for paging, intercom type communications and speaker phone applications. Typically the base unit also includes a microphone. The handset is a typical handset providing a speaker and a microphone.
Telephone systems using distributed networks, such as local area networks (LANs) are also generally known. With these systems, a distributed network is provided, such as carrier sense multiple access with collision detection (CSMA/CD) (see IEEE 802.3) generally known as Ethernet. A telephone network system is provided with a central box having line cards connected to the distributed network as well as network devices connected to the network. The network devices include network telephones with, for example, a base unit with a speaker and a microphone and a handset (with a speaker and a microphone). Data packets are sent over the network between network devices. A network control processor or network call processor (NCP) may be used to monitor and control the access to the PSTN and other connections.
Systems may be provided with a system network chassis or box that provides power to various units such as the NCP, line cards and for example other cards such as a system network card. The chassis may typically include a backplane with a power bus and with an Ethernet bus providing a communication path between the NCP and the line cards and the system network card (if any). The system network card may be connected to the Ethernet network with other network devices similarly connected to the Ethernet network. Traffic between the NCP and the line cards passes over the Ethernet bus provided in the chassis. Traffic to the other network devices, such as to network telephones, is sent from the Ethernet bus of the chassis to the Ethernet network. The Ethernet network is established for example with a 10BaseT implementation of IEEE 802.3 Ethernet over unshielded twisted pair wiring with RJ connectors with each node connected to a central wiring center (a hub, router, switch etc.). The implementation may be for example both Ethernet and fast Ethernet (data transfer rate of 100 Mbps).
The use of a chassis with a backplane presents significant advantages with regard to using modular components. Different components may be added and removed, allowing swapping and changing. The backplane provides further communication paths between the modular components. However, the backplane Ethernet path presents a limitation as to the use of the chassis for cards which require a great deal of bandwidth.